1. Field of the Invention
The present invention relates generally to wire-grid polarizers for physically decoupling two orthogonal porlarizations of visible or near-visible light. More particularly, the present invention relates to a corrosion resistant wire-grid polarizer, and a method for treating such a wire-grid polarizer to resist reactivity.
2. Related Art
Wire-grid polarizers have been developed that are operable in the visible and near-visible spectrum of electromagnetic radiation or light to generally decouple the two orthogonal polarizations of the light. Such wire-grid polarizers can be useful in optical systems such as image projections systems and image display systems.
Concerns exist, however, about the durability or long-term integrity of the wire-grid polarizers. Specifically, it is a concern that the conductive elements may be susceptible to corrosion or deterioration, especially in situations or applications where humidity or moisture and heat are present. It will be appreciated that the extremely small size of the grids may make the grids more susceptible to corrosion, or may exacerbate the results of such corrosion. The corrosion of the grids can reduce or destroy the ability of the grids to decouple the orthogonal polarizations of the light, thus defeating the purpose of the polarizer. In addition, the corrosion of the grids can detrimentally affect or alter the properties of the light, thus frustrating the operation or performance of the optical system.
Simply encapsulating the grids in order to protect the grids raises additional concerns. In addition to decoupling the orthogonal polarizations of light, it also is desirable that the wire-grid polarizer otherwise unalter the light. The material used to encapsulate the grids can create an interface between the material and the elements or the substrate that can alter various properties of the polarizer. Thus, encapsulating the grids might protect the elements, but also might undesirably alter other properties of the polarizer, thus affecting properties of the light, again frustrating the operation or performance of the optical system.
It has been recognized that it would be advantageous to develop a polarizing device, such as a wire-grid polarizer, that decouples orthogonal polarization of visible and near-visible light, resists corrosion or reactivity, and that otherwise does not undesirably alter the light. In addition, it has been recognized that it would be advantageous to develop a method for fabricating such a wire-grid polarizer, or for treating such a wire-grid polarizer, to resist corrosion or reactivity, without otherwise undesirably altering the light, and which is inexpensive.
The invention provides a corrosion resistant polarizer device, such as a wire grid polarizer, for generally decoupling two orthogonal polarizations of electromagnetic waves within wavelengths within the range of ultraviolet, visible and infra-red, such as visible visible light. The polarizer device can include an optical element with a nano-structure. The optical element can include a transparent substrate having an optical property of transmitting the electromagnetic waves or visible light therethrough. The nano-structure can include an array of spaced-apart, elongated elements disposed on the substrate. The elements can be sized to interact with electromagnetic waves of the electromagnetic waves or visible light to generally transmit electromagnetic waves of one polarization, and generally reflect electromagnetic waves of another polarization. A substantial mono-layer advantageously can be chemically bonded to, or reacted with, the elongated elements, or a native oxide layer on the elements, without substantially adversely effecting the optical property of the transparent substrate to transmit the electromagnetic waves or visible light, and without substantially adversely altering the electromagnetic waves or visible light transmitted through the array of spaced-apart, elongated elements and the transparent substrate. The mono-layer can be formed from a corrosion inhibitor, and can have a thickness less than approximately 100 Angstroms.
In accordance with a more detailed aspect of the present invention, the corrosion inhibitor can include, or the mono-layer can be formed from, an amino phosphonate applied to the elongated elements. The amino phosphonate can include a nitrilotris (methylene) triphosphonic acid, or NTMP. The amino phosphonate and the polarizer device advantageously can be heated together to a temperature greater than approximately 150 degrees Celsius.
A method for resisting corrosion of elements of the polarizer device, or to fabricate the polarizer device, includes the step of chemically bonding a corrosion inhibitor to the elongated elements to form a layer having a thickness less than approximately 100 Angstroms. The layer can be formed on, and chemically bonded to, the elements by applying an amino phosphonate to at least the elongated elements, such as by dipping or soaking the polarizer device in the corrosion inhibitor. The polarizing device can be dipped and soaked in a solution of nitrilotris (methylene) triphosphonic acid (or NTMP). In addition, the polarizer device can be heated at a temperature greater than approximately 150 degrees Celsius.
Additional features and advantages of the invention will be apparent from the detailed description which follows, taken in conjunction with the accompanying drawings, which together illustrate, by way of example, features of the invention.